The present invention relates to a deposition mask, a method for manufacturing a display unit using same, and a display unit. More specifically the present invention relates to a deposition mask suitable for manufacturing a display unit using organic light emitting devices, a method for manufacturing a display unit using same, and a display unit.
In recent years, as a display unit instead of a liquid crystal display, an organic light emitting display which uses organic light emitting devices has been used. The organic light emitting display has characteristics that its viewing angle is wide and its power consumption is low since it is a self-luminous type display. The organic light emitting display is also thought of as a display having sufficient response to high-definition high-speed video signals, and is under development toward the practical use.
A conventional organic light emitting display is manufactured through processes of FIGS. 1 to 7. First, as shown in FIG. 1, a number of first electrodes 114 are formed on a substrate 111. These first electrodes 114 are patterned for respective organic light emitting devices, and electrically connected to unshown TFTs (Thin Film Transistor) which are provided corresponding to respective organic light emitting devices with an unshown planarizing layer in between.
Next, as shown in FIG. 2, an insulating film 115 is formed in an area between the number of first electrodes 114. This insulating film 115 is provided with openings 115A corresponding to the first electrodes 114.
Subsequently, as shown in FIG. 3, an auxiliary electrode 116A is formed at the position corresponding to the inside of picture on the insulating film 115, and a trunk-shaped auxiliary electrode 116B which becomes a bus line for the auxiliary electrode 116A is formed in a peripheral area of the substrate 111. The auxiliary electrode 116A is provided in order to uniform a wiring resistance between a power source (not shown) and respective light emitting parts, and inhibit generation of emission unevenness due to difference of voltage drop (particularly emission unevenness between a central part and a peripheral part inside the picture). Further, on an end of the trunk-shaped auxiliary electrode 116B, an extraction electrode 116C is provided in order to connect a second electrode 116 to the power source.
After that, for example, an organic layer 117 of an organic light emitting device 110G generating green light is formed as shown in FIG. 5, by using a deposition mask 140 having openings 141 corresponding to respective organic light emitting devices as shown in FIG. 4.
Next, as shown in FIG. 6, an organic layer 117 of an organic light emitting device 110R generating red light is formed by moving the deposition mask 140, and as shown in FIG. 5, an organic layer 117 of an organic light emitting device 110B generating blue light is similarly formed by moving the deposition mask 140 again.
Subsequently, as shown in FIG. 7, the second electrode 116 is formed almost over the whole area of the substrate 111 by deposition method. The second electrode 116 and the auxiliary electrode 116A are thereby electrically connected at a contact part 118.
Conventionally, for example, a case wherein a rib which serves as a spacer for a deposition mask to form an organic layer is provided between respective organic light emitting devices, and an auxiliary electrode is formed on this rib has been proposed. See, for example, Japanese Unexamined Patent Application Publication No. 2001-195008.
In the conventional deposition mask 140, the openings 141 are provided corresponding to respective organic light emitting devices (FIG. 4). When deposition is performed by using such a deposition mask 140, a film thickness distribution may be generated in the organic layer 117 depending on conditions of deposition from an evaporation source 152, as shown in FIG. 8. Such a film thickness distribution varies depending on a plate thickness or a cross sectional shape of the deposition mask 140, or a physical relation between the evaporation source 152 and the openings 141 of the deposition mask 140. In particular, the film thickness distribution is subject to influence by characteristics of the evaporation source 152. Light emitting colors, that is, light emitting wavelengths of the organic light emitting devices depend on a film thickness of the organic layer 117. Therefore, in order to prevent color unevenness inside pixels, it is necessary to utilize only the area in the vicinity of the center of the organic layer 117 having an even film thickness as an effective light emitting region 117A. Therefore, there has been a problem that when using the conventional deposition mask 140, the effective light emitting region 117A is limited, so that an aperture ratio is lowered.